Cemented carbide material comprises particles of metal carbide such as tungsten carbide (WC) or titanium carbide (TiC) dispersed within a binder material comprising a metal such as cobalt (Co), nickel (Ni) or metal alloy. The binder phase may be said to cement the carbide particles together as a sintered compact. Measurements of magnetic properties may be used to measure indirectly aspects of the microstructure and properties of cemented carbide materials. The magnetic coercive force (or simply coercive force or coercivity) and magnetic moment (or magnetic saturation) can be used for such purposes.
Cemented carbides have a relatively high fracture toughness and hardness, and so are used in tools that exploit these properties. Examples of such tools include picks for road planing or mining applications. However, the hardness and wear-resistance of WC—Co cemented carbides usually can be improved only at the expense of fracture toughness and strength (Konyashin, “Cemented Carbides for Mining, Construction and Wear Parts”, Comprehensive Hard Materials, Elsevier Science and Technology, 2014). It is therefore difficult to simultaneously improve hardness, wear-resistance, fracture toughness and transverse rupture strength (TRS) of cemented carbide materials.
One possible approach to improve both the hardness and fracture toughness is the fabrication of cemented carbides with a uniform microstructure containing rounded WC grains. U.S. Pat. No. 6,126,709 discloses such a cemented carbide material, in which the microstructure is coarse and very uniform containing large rounded WC grains. A disadvantage of this material is the presence of very thick Co interlayers around the large, rounded WC grains. The thick Co interlayers are characterized by low hardness and wear-resistance and therefore tools using this type of material quickly become worn during rock-cutting or rock-drilling operations. This leaves unsupported WC grains, which can be easily cracked, destroyed and detached resulting in high wear rates (Konyashin et. al., “Novel Ultra-Coarse Hardmetal Grades with Reinforced Binder for Mining and Construction”, International Journal of Refractory Metals and Hard Materials, 23(2005)225-232).
One approach to mitigate the low wear-resistance of thick Co interlayers in ultra-coarse WC—Co materials mentioned above is suggested in WO2012/130851A1. This discloses a cemented carbide material in which the binder interlayers are hardened and reinforced by nanoparticles having a composition according to the formula CoxWyCz. The cemented carbide material disclosed in WO2012/130851A1 is characterized by a very low carbon content and consequently low magnetic moment, which is known to lead to the suppression or complete elimination of the dissolution and the re-crystallization of fine-grain WC fraction usually present in initial WC powders during liquid-phase sintering (see Konyashin et. al., “On the Mechanism of WC Coarsening in WC—Co Hardmetals with Various Carbon Contents”, International Journal of Refractory Metals and Hard Materials, 27 (2009) 234-243). As a result, the microstructure of the cemented carbides disclosed in WO2012/130851A1 is characterized by relatively low uniformity and contains much of the fine-grain WC fraction present in the original ultra-coarse WC powder, which leads to their reduced fracture toughness.